This invention relates to a method and also to an associated apparatus for examining structural members for purposes of detecting hidden defects.
Architectural and vehicular structural members such as bridge girders, columns, floor and roof support beams, airplane wings, and other architectural and vehicular stress-bearing members can suffer failure arising from invisible defects. Not infrequently, stress fractures and fatigue cracks originate internally to a support member and are not detectible even by the most sensitive and rigorous of existing testing techniques. Such defects may result in dangerous, even fatal, accidents irrespective of the diligent care taken by maintenance personnel.
It is not uncommon for aging structures to be destroyed or discarded for fear of structural failure even though the structures may still have many years of useful life, unbeknownst to the owners. This premature retirement of buildings, bridges, planes, train cars , etc., is generally a waste of public and private assets and thus contributes to rising costs and depleting resources.
Even where architectural and vehicular assets are maintained, structural investigations are time consuming and expensive. The necessary expense is particularly evident where the investigated structures must be disassembled and transported to testing facilities. Detecting hidden defects without disassembly of the structures is even more difficult when the structures cannot be disassembled, for example, in the cases of buildings and bridges.
A method for investigating structural integrity in accordance with the present invention utilizes a carrier member having a flexible surface and a plurality of electromechanical transducer elements attached to the carrier member, the transducer elements being spaced from each other along at least two spatial dimensions. The method comprises conforming the flexible surface to a solid structural member, so that a substantial portion of the flexible member is in effective wave-transmitting engagement with the structural member, thereafter transmitting energization or diagnostic pressure waves into the structural member, receiving pressure waves reflected from an internal structural defect in the structural member in response to the pressure waves transmitted into the structural member, and analyzing the received pressure waves so as to detect the structural defect.
Pursuant to another feature of the present invention, the method further comprises generating a signal encoding an image of the structural defect from the analyzed pressure waves and presenting the image on a display. It is contemplated that the analyzing of the incoming or reflected pressure waves is implemented by operating a specially programmed general-purpose or dedicated digital computer. That computer may be further operated to highlight a selected feature of the structural defect on the display. The highlighting of the structural defect may include varying video image intensity in a portion of a video image on the display. In addition, the computer may be operated to select the displayed image from among a multiplicity of possible images of the structural defect. For instance, the structural defect may be viewed from any of a number of different angles and magnifications. Parts of the defect may be stripped away or filtered out to enable viewing of internal parts of the defect.
These functions are carried out in part by analyzing the incoming or reflected pressure waves to construct a three-dimensional electronic model or analog of the detected structural defect. The electronic model or analog may then be manipulated by conventional three-dimensional programming to rotate the defect about three Cartesian axes and to magnify the defect in whole or in part.
In order to detect a microscopic defect, the incoming or reflected pressure waves are processed to construct any microscopic structures in the memory of the computer. Detected microscopic structures are then analyzed, for example, by pattern recognition techniques and mathematical operations to determine whether the structures are potential sources of structural failure. Thus, the analyzing of the received pressure waves includes operating the computer to perform an automated diagnosis or evaluation of the structural defect based in part on the digital or electronic model of the structural defect. The performance of the automated diagnosis or evaluation of the structural defect may include operating the computer to automatically compare the digital or electronic model with digital or electronic models of known structural defects stored in a memory of the computer. Any suspect structural anomalies may be reported to a user, for instance, by the display, by print-out, audible signal, etc.
In accordance with another feature of the present invention, the carrier member includes a flexible web. The flexible surface is a surface of the web, the conforming of the flexible surface to the structural member including the step of wrapping the web around at least a portion of the structural member. Where the transducer elements are mounted to the web, the conforming of the flexible surface to the structural member includes placing the transducer elements in contact with the structural member. This procedure is especially effective when the structural member has a substantially smooth outer surface.
An apparatus, described in detail below, for carrying out the method of the invention, is easily portable. Moreover, in testing a large structural member such as a bridge girder or airplane wing, the carrier member is simply removed from one section of the structural member and reapplied to another section of the structural member until essentially the entire member has been examined.
Where the carrier member includes at least one substantially rigid panel and a flexible web connected to the panel to form a bag along the panel, the flexible surface being a surface of the web, the conforming of the flexible surface to the structural member includes (a) placing the flexible web in contact with the structural member and (b) feeding a fluid to the bag to press the web against the structural member. In this procedure, where the transducer elements are mounted to the web, the conforming of the flexible surface to the structural member also includes placing the transducer elements in contact with the structural member.
Where the panel is one of a plurality of panels of the carrier member, the conforming of the flexible surface to the structural member includes (i) placing the bag so that the flexible surface faces the structural member and so that the panels are disposed on an outer side of the bag, away from the structural member and (ii) fastening the panels to one another about the structural member to limit expansion of the bag upon feeding of the fluid thereto. Thus, the panels serve as a restraint ensuring an effective pressure-wave transmitting contact between the flexible surface of the bag and the structural member. It is to be noted in this regard that at least some of the transducer elements may be disposed on the panel. In that case, the fluid fed to the bag is a liquid, so that the transmitting of the pressure waves from at least one of the transducer elements into the structural member includes transmitting the pressure waves through the liquid in the bag. The liquid may thus serve not only a pressurizing function but also as a medium for pressure wave transmission.
The fastening of the panels of the carrier member about the bag and concomitantly about a section of the structural member may be implemented by any suitable means including, but not limited to, straps, clasps, buckles, hook and loop fasteners (VELCRO(trademark)), and hooks and eyelets. Generally, the panels are fastened about the structural member prior to pumping or siphoning of liquid into the bag.
It is contemplated that many structural members to be tested by the method and apparatus of the present invention will have several sides extending at angles with respect to one another. In such a case, the conforming of the flexible surface to the structural member includes placing the flexible surface in engagement with at least two surfaces of the structural member extending at a substantial angle relative to one another.
The pressure waves transmitted into the structural member and received as reflections from internal substructures thereof may have a plurality of different frequency ranges. The different frequency ranges have different penetration characteristics, as well as different resolving powers. The use of different frequency ranges provides a greater amount of raw data for analysis and diagnosis of internal irregularities of structural members.
Where the transducer elements are mounted to the carrier member in a predetermined array, the method may further comprise the step of energizing the transducer elements in a predetermined sequence.
An apparatus for investigating defects in structural members comprises, in accordance with the present invention, a carrier member having a flexible surface, the carrier member including a pressurizable bag for conforming the flexible surface to a solid structural member so that a substantial portion of the flexible member is in effective wave-transmitting engagement with the structural member. The apparatus additionally comprises a plurality of electromechanical transducer elements attached to the carrier member, the transducer elements being spaced from each other along at least two spatial dimensions. A frequency generator is operatively connected to at least a given one of the transducer elements for energizing that given transducer element to transmit pressure waves into the structural member. A frequency processor is operatively connected to at least another one of the transducer elements to process pressure waves received by that other transducer element from an internal structural defect in the structural member in response to the pressure waves transmitted from the given transducer element. The processor includes means for analyzing the received pressure waves to detect the structural defect.
Pursuant to another feature of the present invention, the apparatus further comprises an expansion restrictor surrounding the bag for limiting outward expansion thereof in a direction opposite the structural member. As described above, the expansion restriction may include a plurality of rigid panels movably connected to one another and locks or fasteners operatively connected to the panels.
According to another aspect of the invention, the apparatus also comprises an imaging component generating a signal encoding an image of the structural defect from the analyzed pressure waves, the imaging component being operatively connected to a display for presenting the image to a viewer or operator.
The processor preferably includes generic digital processing circuits modified by programming for deriving a digital or electronic model of the structural defect from the analyzed pressure waves. The process may additionally include programming-modified generic digital processing circuits for executing an automated diagnosis or evaluation of the structural defect based in part on the digital or electronic model of the structural defect.
The transducer elements may be all mounted to the bag along a flexible panel thereof, all mounted to rigid panels, or partially mounted to a flexible panel and a rigid panel. Where the transducer elements are attached to a flexible web, at least some of the transducers are placed directly in contact with the structural member under test.
It will be recognized that the processor or wave analyzer must be provided with data from which the relative positions of the transducer elements can be ascertained. This data may be generated by a separate system of position sensors or from signals generated and sensed by the transducer elements themselves.
The present invention facilitates an examination of structural members such as bridge girders, columns, floor and roof support beams, airplane wings, and other architectural and vehicular stress-bearing structures. An apparatus and a related method for investigating integrity of structural members in accordance with the present invention enables the detection and identification of sources of potential structural failure, even where those sources are only in their nascent stages of development.
An apparatus and an associated method for investigating integrity of structural members in accordance with the present invention is portable and utilizable in many applications in situ, without necessitating a deconstruction or disassembly of the structure being investigated. A structural examination or investigation as contemplated herein facilitates the maintenance of architectural and vehicular bodies, reduces costs of investigation, and enables a differentiation of different defects or structural irregularities.